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.cursor/rules/testing.mdc

Cursor testing rule for Rust

A Cursor `.mdc` rule can attach only when you touch tests. This variant keeps testing policy out of the always-on project rule so day-to-day edits stay quieter. This copy is written for a Rust project. This repository is a Rust crate on Cargo. Format with rustfmt, lint with cargo clippy, and use Result for recoverable failure.

The example uses a balanced, readable style, pragmatic tests, and comments only where the intent is not obvious. Open the generator to make the agent stricter, switch to test-first, quiet the comments, or pick a different file.

The example assumes a Cargo crate, edition 2021 or newer. It does not assume a web framework or async runtime. Use thiserror or anyhow only when that crate is already a dependency.

Customize in the generatorBrowse the library

Example file

Balanced strictness, readable style, pragmatic tests. Download name: testing.mdc

---
description: "Testing rules for a Rust repository"
globs: "**/tests.rs"
alwaysApply: false
---

# Testing rules

Attach these rules when editing tests in this Rust repository.
The always-on project rule still lives in `.cursor/rules/project.mdc`. This file does not repeat it.

## Stack

This repository is a Rust crate on Cargo. Format with rustfmt, lint with cargo clippy, and use Result for recoverable failure.

## Commands

- Test: `cargo test`
- Format: `cargo fmt`
- Lint: `cargo clippy --all-targets -- -D warnings`
- Build: `cargo build`

Use the script the repo already defines when it differs from the command above.

## Testing

Add or update tests when behavior changes.

Add unit tests beside the function you changed. Cover the Ok path and one Err path.

## Done when

- The requested behavior works.
- `cargo test` passes. Run `cargo clippy --all-targets -- -D warnings` when the change is more than a comment.
- The diff stays inside the task.
- You list anything you could not run.

Add it to the project

  1. 01

    Copy a starting file

    Copy the example Cursor testing rule on this page, or open the generator if you want different testing, strictness, or comment rules.

  2. 02

    Save it at .cursor/rules/testing.mdc

    Save it at `.cursor/rules/testing.mdc` in the Rust repo, next to the always-on project rule. Leave `alwaysApply` false so it only joins test edits.

  3. 03

    Start a fresh agent session

    Rules files are read when a session starts. A chat that is already open may still be using the old instructions.

  4. 04

    Give it one small task

    Ask for one change a Rust agent often gets wrong, such as a function that returns Result instead of unwrap on library input. If it ignores the file, confirm the path and start a new session.

Questions about this file

Where do I put Cursor testing rule in a Rust repo?

Save it at `.cursor/rules/testing.mdc` in the Rust repo, next to the always-on project rule. Leave `alwaysApply` false so it only joins test edits.

Which tools read this Cursor testing rule?

Cursor loads `.cursor/rules/testing.mdc` when a file matches its globs. It does not replace `project.mdc`. Keep the always-on rule for stack conventions.

What does the Rust example assume?

The example assumes a Cargo crate, edition 2021 or newer. It does not assume a web framework or async runtime. Use thiserror or anyhow only when that crate is already a dependency.

Does VibeSpell upload my repository?

No. Recipe pages are static, and the generator builds the file in your browser from the options you pick. Your source code never leaves the machine.

Other files for Rust

Cursor testing rule for other stacks